Data transfer system

Abstract

In a data transfer system in which when a first to fourth terminals require reading data, the data are read out of a first to fourth storages to be stored in a first and second buffer memories while a first and second virtual groups of storages are alternately switched every constant cycle, and thereafter a first and second data sending units send the data stored in the first and second buffer memories to the terminals; on the other hand, when the first to fourth terminals require writing data, received data is divided in a way to distribute the process loads of data read and data write of the divided data equally into a first and second data transfer units. At the same time, the data are stored in the first and second buffer memories of the first and second data transfer units, and thereafter the data are written into the first to fourth storages while switching the first and second virtual groups of storages alternately. As a result, the load of transferring data to the terminals is not concentrated on a particular data transfer unit in the data transfer system, even when the rate of request-to-reads from the terminals changes or differs from those of others.

What is claimed is: 
     
       1. A data transfer system comprising: a plurality of data transfer paths comprising a group of storages including a plurality of storages for storing data, an accumulating unit for temporarily accumulating said data to be transferred which are stored in said storages, a storing unit for reading out said data to be transferred stored in said storages to store said data to be transferred in said accumulating unit, and a transferring unit for transferring said data to be transferred stored in said accumulating unit to terminals, thereby dividing a file into a plurality of blocks having a given size to distribute said blocks into said plural storages on said different data transfer paths for storing said blocks, receiving request-to-reads from said terminals connected to ends of said data transfer paths by read request receiving units to properly read said data out of said storages and thereafter to transfer said data into said terminals;   a plurality of virtual groups of storages comprising storages which are those selected from said storages on said different data transfer paths; and   data transfer controller for, at the first period, reading said distributed data, which are stored in a given virtual group of storages among said plural virtual groups of storage, from said storages on said plural data transfer paths all at once, to store said read data in said accumulating unit, and then at the second period, reading said distributed data, which are stored in a virtual group of storages different from said given virtual group of storages, from said storages on said plural data transfer paths all at once, to store said read data in said accumulating unit, and thus successively changing said virtual groups of storages to read data therefrom by alternating said first period and said second period.   
     
     
       2. The date transfer system of claim 1 which includes a write request receiving unit for receiving data of request-to-writes from said terminal to divide said received data into a plurality of data blocks the number of which corresponds to the number of said plural data transfer paths and then to write said divided data into said respective storages constituting said virtual group of storages, said write request receiving unit, at the first period, writing data into storages constituting a given virtual group of storages among said plural virtual groups of storages, and then at the second period, writing data into storages constituting a virtual group of storages different from said given virtual group of storages; and which includes a data write changing unit for successively changing said virtual groups of storages to write data therein by alternating said first period and said second period. 
     
     
       3. The data transfer system of claim 2 which includes a plurality of said write request receiving units and said data transfer controller including a designating unit for designating, in advance, which of said plural write request receiving units receives and processes data of request-to-writes from which terminal. 
     
     
       4. The data transfer system of claim 2 which includes a plurality of said write request receiving units and a write request controller for receiving request-to-write-datas from said terminals to calculate the load rates of processing request-to-write-datas which is being processed by said respective write request receiving units, and according to said calculated result, transferring said request-to-writes to said write request receiving unit having the lowest load rate. 
     
     
       5. The data transfer system of claim 1 which includes a write request controller for receiving request-to-write-data from a terminal to divide said received request-to-write-data into a plurality of request-to-write-datas the number of which corresponds to the number of said data transfer paths, and then transferring said divided request-to-write-datas to said respective data transfer paths, and which includes received data storing units, which are set up on said respective data transfer paths, for receiving said request-to-write-datas transferred from said write request controller to store said received data in said accumulating unit.